AoA Indicator

[Chimpanzee]

Actually a  remark of Hank in another topic (Serviceability of Glass Panels)  triggered this one.

I have always been interested in an AoA indicator. Guess that comes from reading Aerodynamics for Naval Aviators and from doing a few hours in gliders. When I bought my (old) Mooney M20C, an AoA indicator was one of the things I really wanted to put in it. Somehow I haven't gotten around to that yet (other needed things took precendence). But flying out of Falcon Field Mesa (FFZ) and into higher terrain airports, it would be a good thing to have.

The only indicator that I have seen for GA so far is the Alpha System.
Does anybody out there have experience with these units. How are they calibrated to the specific aircraft model? Or, are there any other manufacturers?

Grateful for any input.

Norbert

M20C (1963)

[jimosborn]

Norbert, there has been a huge amount of information on AoA for GA published within the past two years, largely the result of research and mentoring by Fred Scott from VA and Tom Rosen from CA who were motivated to take up the mantle and "do something" by the loss of two close friends each, veteran pilots all, who succumbed to turn-to-final stall spin accidents.

 

In collaboration with Mark Korin of Alpha Systems, AOPA Safety Foundation, FAA and a host of volunteer professionals, including retired professor Dr. David Rogers who taught at the Naval Academy and is intimately familiar with Aerodynamics for Naval Aviators, Fred & Tom embarked on a mission to educate and encourage the use of AoA by the GA community.

 

Inasmuch as Fred and Tom are both Beech owners (King Air and Bonanza respectively), most of this has been posted on Beech-Talk and Beech-list.org forums.  Here's the link to Fred's website with many subjects internally cross-linked. 

 

http://www.ballyshannon.com/aoa.html  

 

Welcome, and congratulations on your timely interest in the world of practical AoA systems. 

 

Jim Osborn 

[201er]

My plane came with an AOA. I didn't appreciate it enough at first but it has saved my skin several times. It is most helpful when flying at unfamiliar weight configurations but it is also:

 

-A backup airspeed indicator (in case of pitot malfunction, icing, or other problem)

-A good indication of stall safety margin in turns during slow flight

-Could be a life saver in an icing condition where pilot does not know what speed to fly

 

During a flight today I had my door pop open after departure (long story for another time) and the plane flew very different on final. I trusted the AOA rather than the ASI and flew a higher speed as a result and made it back safely. I have also been close to stall in steep turns (particularly heavy loaded) in the pattern in the past and the AOA made me aware of this. I have 100 gallon tanks and frequently go from carrying 300-980lbs of load depending how full the tanks are. ASI tells you nothing for these conditions but AOA is great to have.

 

Come to think of it, AOA is probably a better investment than a traffic advisory system considering how many midairs vs stalls occur.

[carusoam]

Hardware price looks under $500?

Installation not priced, but appears that it can put into an existing 6" round panel.

Mike, any details on your installation?

Best regards,

-a-

[Oscar Avalle]

I installed one in my m20c but I have not been able to calibrate the unit. I must say I feel rather frustrated. I follow the instructions but it tells me that I have to adjust the probe but the iris no more room to do so.

Sent from my iPad using Tapatalk HD

[201er]

Mine came with the plane. It's called a Safe Flight SC-150. It is driven by what looks like a stall warning tab on the wing but it displays the range rather than just a warning. I have no idea what it costs to install one but I laugh at the idea of having a second 430 GPS before a AOA!!!

[DaV8or]

I'm very interested in a AoA indicator. I spoke at length with the owner of Alpha systems at the AOPA Summit. I liked everything I heard except the way it is calibrated. The process is a little fuzzy and not as accurate as I would like. Basically, you install the system wherever within certain areas, then you have to go out and fly certain flight profiles and when you think you are in the zone based on your pitot static gauges, a passenger presses a little button on the unit to give it a base line.

 

Seems a little, well, unprecise to me. Are you really on the edge of stall? Maybe you're closer than you think. I guess I was hoping there was a more mathematical, or geometric way to calibrate it on the ground and be certain where the stall is.

[M016576]

<blockquote class='ipsBlockquote'data-author="DaV8or" data-cid="87105" data-time="1358131780"><p>

I'm very interested in a AoA indicator. I spoke at length with the owner of Alpha systems at the AOPA Summit. I liked everything I heard except the way it is calibrated. The process is a little fuzzy and not as accurate as I would like. Basically, you install the system wherever within certain areas, then you have to go out and fly certain flight profiles and when you <em class='bbc'><strong class='bbc'>think</strong></em> you are in the zone based on your pitot static gauges, a passenger presses a little button on the unit to give it a base line.<br />

<br />

Seems a little, well, unprecise to me. Are you really on the edge of stall? Maybe you're closer than you think. I guess I was hoping there was a more mathematical, or geometric way to calibrate it on the ground and be <strong class='bbc'>certain </strong>where the stall is.</p></blockquote>

It's almost Test Pilot level to get that right on the first try (IMO). Luckily repeating the procedure is fairly simple (or so it seems according to the literature). Regardless, if its properly calibrated, I'd LOVE to have one, and as soon as I get the 1300 or so for the 2-1/2" ultra, I will.

[jimosborn]

I installed one in my m20c but I have not been able to calibrate the unit. I must say I feel rather frustrated. I follow the instructions but it tells me that I have to adjust the probe but the iris no more room to do so.

Sent from my iPad using Tapatalk HD

 

Oscar, sorry I don't have the Alpha Systems install manual handy, but in situations like you describe I recall there are instructions that allow elongating the mounting slot if that becomes necessary.  It shouldn't be at all difficult to do; just make sure that everything else has been done in sequence and the system is ready for calibration.

 

Cheers!

[jimosborn]

I'm very interested in a AoA indicator. I spoke at length with the owner of Alpha systems at the AOPA Summit. I liked everything I heard except the way it is calibrated. The process is a little fuzzy and not as accurate as I would like. Basically, you install the system wherever within certain areas, then you have to go out and fly certain flight profiles and when you think you are in the zone based on your pitot static gauges, a passenger presses a little button on the unit to give it a base line.

Seems a little, well, unprecise to me. Are you really on the edge of stall? Maybe you're closer than you think. I guess I was hoping there was a more mathematical, or geometric way to calibrate it on the ground and be certain where the stall is.

 

Slow flight, but not at all on the edge of stall, nor is calibration imprecise... the one-time baseline calibration procedure is designed strictly to define Optimum Angle of Attack (OAA) and consists of determining the point at which, at any given power setting, the airplane is neither climbing or descending.

The logic, as I understand it, is that this establishes a data point from which actual stall AOA plus every other user-defined calibration point will be accurate within a very narrow range, regardless of weight, wing loading etc. Moreover, the user may redefine his/her calibration points at will.

Aural alerts (especially "Slow Sarah" sweetly saying "getting slow"... whenever that's the case) are exclusive to Alpha Systems electronic units, and in my opinion, a truly immeasurable safety feature since the single most common - and deadly - aspect of stall-spin accidents is distraction.

Cheers!

[Oscar Avalle]

I installed one in my m20c but I have not been able to calibrate the unit. I must say I feel rather frustrated. I follow the instructions but it tells me that I have to adjust the probe but the iris no more room to do so.

Sent from my iPad using Tapatalk HD

Oscar, sorry I don't have the Alpha Systems install manual handy, but in situations like you describe I recall there are instructions that allow elongating the mounting slot if that becomes necessary. It shouldn't be at all difficult to do; just make sure that everything else has been done in sequence and the system is ready for calibration.

Cheers!

thanks will do so...

Sent from my iPad using Tapatalk HD

[Chimpanzee]

Jim,

thanks for all the input and the link which was very useful. A lot of good work by dedicated people. I am stil working my way through the flight test reorts, and need to check how to install it on my 20 C, but it looks like the Legacy AoA is way to go.

Norbert

[xftrplt]

-Could be a life saver in an icing condition where pilot does not know what speed to fly

While I agree on the value of AoA indicators (never looked at the ASI in the overhead pattern in the F-4--just flew to the steady tone at 19.2 units, or the fast beep indicating more than 20 ), icing is one condition where it is NOT to be trusted...at least as normally used.

In fact, some air transports--I believe the ATR series is one--have a lower AoA band for icing.  Quite simply, with the airfoil shape distorted, a stall will occur at a lower AoA than clean.  Caveat aviator.

[DaV8or]

While I agree on the value of AoA indicators (never looked at the ASI in the overhead pattern in the F-4--just flew to the steady tone at 19.2 units, or the fast beep indicating more than 20 ), icing is one condition where it is NOT to be trusted...at least as normally used.

In fact, some air transports--I believe the ATR series is one--have a lower AoA band for icing.  Quite simply, with the airfoil shape distorted, a stall will occur at a lower AoA than clean.  Caveat aviator.

 

In addition, I don't think the mast on the Alpha unit anyhow is heated. So it can ice over just like an un heated pitot tube can.

[jimosborn]

Actually Alpha Systems does offer an optional heated mast; I know Fred Scott has it on his King Air.